1. Field of the Invention
The present invention is directed generally to an electromagnetic relay having a leaf spring secured to the armature and carrying contacts on a portion of the spring extending beyond a free edge of the armature.
2. Description of the Related Art
Numerous type of relays are known including relays such as those disclosed in, for example, German Published Application 35 28 715 A1 or European Published Application 0 113 440 A1. The relays disclosed in these references are of an extremely simple design since there is a direct connection between the armature and the contact spring which avoids the use of an additional slide and wherein the contact spring frequently also provides the bearing and restoring force on the armature. These relays have two contact pieces on the free end of the contact spring and, thus, may be used as a bridge contact or as a double contact. The contact pieces are mounted on transverse legs on the free end of the contact spring which results from a constriction in the width of the contact spring between the fastening location of the contact spring on the armature and the transverse legs. This constriction causes the spring to have a soft spring characteristic, or low spring modulus, while at the same time allows for spring flex to compensate for variations in contact positions when switching.
Since double contact or bridge contact relays generally serve to switch higher currents, errors in relay switching and, thus, device outages may occur during use as a result of fusing or sticking of the contacts. The forces which act on so-called make-contacts through the contact spring when the armature drops off, or opens, may be inadequate under certain circumstances to pull apart slight welding or fusing of the contact surfaces. This is due to the opening forces of the armature being highly damped as a consequence of the susceptibility of the spring to flexing in both the longitudinal and transverse directions at the constriction. Thus, the opening forces are not fully transmitted to the adhered contact locations.
To avoid these disadvantages, either the spring restoring forces must be increased which in turn requires an increased excitation of the relay and, thus, a higher thermal load on the relay, or a relay of larger dimensions is required.